Impeller adjuster for centrifugal pump

ABSTRACT

A centrifugal pump having an adjustable feature enabling precise adjustment of the impeller&#39;s location.

This is a division of application Ser. No. 408,043, filed Aug. 13, 1982.

BACKGROUND OF THE INVENTION

This invention relates to centrifugal pumps and to an improved impellerposition adjustment feature in such pumps.

Typically, centrifugally pumps have an impeller which is axiallyadjustable but which has no means to determine with precision the exactposition of the impeller.

SUMMARY OF THE INVENTION

In one aspect, the invention features a centrifugal pump having a bladedimpeller in a stationary pump housing, the leading edges of the bladesbeing adjacent a first radially extending wall of the housing, arotatable shaft on which the impeller is mounted, a shaft support forrotatably holding the end of the shaft which is opposite the impeller,and adjustable fastening means for connecting the shaft support to astationary member, the impeller, shaft and shaft support together beingadapted for axial adjustment upon axial adjustment of the fasteningmeans, the fastening means having at least two threaded bolts projectingfrom the stationary member in a direction parallel to the axis of theshaft, and reference nuts for fixing the position of the shaft supporton the bolts, the reference nuts having marks at regular angularintervals, and at least one reference mark on the shaft support adjacenteach reference nut cooperating with the marks on the reference nuts forindicating the axial position of the impeller with respect to the pumphousing.

In preferred embodiments, the impeller has a radially extending faceopposite the leading edges, the pump housing further comprises a secondradially extending wall adjacent the face, and an annular seal ispositioned between the face and the second wall to seal against thesecond wall when the impeller is withdrawn from the first wall to thesecond wall; the seal is mounted on the impeller face; and the two boltsare spaced apart on opposite sides of the shaft.

The impeller blades can be precisely positioned with respect to the pumphousing to assure maximum pumping efficiency, the impeller can berepositioned accurately to accommodate blade wear, and the referencenuts can be used to gauge the total blade wear to determine when theimpeller should be replaced. The annular seal assures that the sealhousing is sealed off from the fluid in the pump housing when theimpeller is withdrawn, so that work can be easily performed in the sealhousing.

Other objects, features and advantages of the invention will be apparentfrom the following description of the preferred embodiments and from theclaims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

We first briefly describe the drawings.

Drawings

FIG. 1 is a side elevation view of the pump assembly.

FIG. 2 is an enlarged sectional view of the pump assembly of FIG. 1 withthe motor and motor adaptor removed, showing one type of seal housing.

FIG. 3 is a view, taken along line 3--3 of FIG. 2.

FIG. 4 is a view, taken along line 4--4 of FIG. 2.

FIG. 5 is a plan view, partly in section and partly broken away, of theseal housing and pump housing.

FIG. 6 is a view, taken along line 6--6 of FIG. 5.

FIG. 7 is an isometric exploded view of a seal housing with alternatecoils attached to the cover.

FIG. 8 is a sectional view similar to FIG. 5 showing an alternative sealhousing containing a packing seal.

FIG. 9 is a view, partially broken away, taken along line 9--9 of FIG.8.

STRUCTURE AND OPERATION

Referring to FIG. 1, in pump assembly 10, pump housing 11 defines animpeller chamber 12 (shown in FIG. 2) in which impeller 14 rotates topump fluid from pump inlet 16 to pump outlet 18. Impeller 14 is mountedon one end of shaft 20, the other end of which is (by means of directmount motor adaptor 22) coupled to and aligned with the shaft of motor24. Behind pump housing 11, shaft 20 is enclosed by a removable sealhousing 26 which is bolted to the backplate 28 of pump housing 11. Alsobolted to pump housing 11 is one end of a bearing frame adaptor 32, theother end of which is bolted to bearing housing 34 (which serves as ashaft support for the end of the shaft opposite the impeller) to assurethe axial alignment of shaft 20, pump housing 11 and bearing housing 34.Adjustable fastening means 36 are positioned behind bearing housing 34for adjusting the axial position of impeller 14. Rear foot 29 and casingfoot 31 support the pump assembly, foot 29 extending on each side of thecenter of gravity of the assembly when disconnected from the impeller.

Referring to FIG. 2, which shows the pump in greater detail, shaft 20 issupported rotatably by a pair of bearings 42, 44 housed within bearinghouse 34. The position of rear bearing 42 is fixed axially with respectto shaft 20 by recessed shaft surface 46 (adjacent the forward end ofbearing 42) and by washer 48 and threaded retainer nut 50 (adjacent therearward end). Bearing 42 is also held fixed within a bearing cartridge62 by retaining surface 64 and by retaining ring 66 which is bolted tothe bearing cartridge. Similarly, the position of front bearing 44 onshaft 20 is set (on the rear end) by recessed shaft surface 52. A springretaining ring 54 (which seats in groove 21 in shaft 20) and retainer 56together force oil seal 58 and coupling ring 60 against the front end ofbearing 44, and assure proper seal compression of seal 58.

The shaft assembly, including shaft 20, bearings 42, 44, bearingcartridge 62, and impeller 14 (which is screwed onto the threaded frontend of shaft 20), is free to be moved axially, because the cylindricalouter surface of the cartridge housing 62 is free to slide in thecylindrical bearing housing bore 68 in which it is mounted, thecylindrical outer surface of cylindrical bearing 44 is free to slide inthe bearing housing bore 70 in which it is mounted, the cylindricalouter surface of oil seal 58 is free to slide in cylindrical bearingframe adaptor bore 72 in which it is mounted, and shaft 20 is free toslide in the stationary element 74 of seal 76. The axial excursion ofthe shaft assembly is limited in one direction by the radially extendingwall 78 of pump housing 11, which is adjacent to the leading edge 80 ofimpeller 14, and in the other direction by radially extending face 82 ofbackplate 28 which is adjacent to the trailing edge 84 of impeller 14.

The axial position of the shaft assembly is determined by adjustablefastening means 36 which comprise two bolts 100 (e.g., 1/2-20 or 1/2-13)which pass through clearance holes 102 in bearing cartridge 62 and arefirmly screwed into the back of bearing housing 34, and a reference nut104 and a locknut 106 screwed onto each bolt 100, with the bearingcartridge between them, so that they can be tightened down onto thebearing cartridge to adjust and fix its axial position.

Referring to FIG. 3, each reference nut has a rim portion 108 on whichmarks 110 are inscribed at regular angular intervals (e.g., 22.5°) andare readable in connection with reference marks 112 on bearing housing34.

In operation, the axial position of the impeller is adjusted so that thegap between edge 80 and wall 78 will provide optimum pumping efficiency,e.g., a gap of 0.015 inch. This is accomplished by loosening referencenuts 104 toward the front of the pump assembly and tightening locknuts106 also toward the front of the pump assembly, until the shaft assemblyreaches an axial position at which the impeller leading edge strikes thepump housing wall 78. The position of each reference nut compared withits associated reference mark 112 is noted. The locknuts are backed offand the reference nuts are then turned back towards the back of the pumpassembly by a number of marks 110 which correspond to the desiredimpeller gap (as determined by the angular spacing between the marks andthe pitch of the threads of bolts 100). As the impeller blades wear, theshaft assembly can be moved forward a precise distance to reposition theimpeller by a similar use of reference nuts 110. By recording the totalamount of such adjustments for wear, it is possible to determine easilywhen the impeller should be replaced. The adjustable fastening means 36also permits backing off the shaft assembly to the point where the rearsurface 84 of the impeller reaches the pump housing wall 82, and when sobacked off an O-ring seal 114 in the back wall of the impeller seals offseal housing 26 from fluid located in the impeller chamber 12, so thatwork can be performed in the seal housing without the presence of thefluid and without need of draining fluid from impeller chamber 12.

Referring to FIGS. 2 and 4, a centrifugal lubricator 40 (of metal orplastic) is positioned in bearing housing 34 for lubricating bearings42, 44. Lubricator 40 is fixed to shaft 20 by set screw 120. Lubricator40 has an annulus 121 with a circular internal tube 122 the inner wallof which is defined by the surface of shaft 20. A tubular passagethrough the outer wall of annulus 121 defines entrance opening 124tangential to the tube. A number of spaced exit openings 126 (orientedradially from shaft 20) in its side pass through the outer periphery ofthe annulus. Mesh screen 128 (e.g., nylon with mesh openings between 50and 300 microns) is arranged around the inner wall of the tube coveringthe exit openings.

The inner surface of bearing housing 34 is contoured to define an oilreservoir 130 containing oil 132 to a level such that oil can enterentrance opening 124 during each rotation of lubricator 40 on shaft 20.Oil which has entered tube 122 is thrown centrifically out through exitopenings 126 (after passing through screen 128, which removes carbon andparticulate contaminants). Oil seals 58 and 130 (housed in the oppositeends of the bearing housing) and oil seal 131 on the outer surface ofbearing cartridge 62 prevent leakage of oil from the bearing housing.

Referring to FIGS. 2 and 5, seal housing 26 contains a mechanical seal76 (e.g., a seal sold by A. W. Chesterton Co., Stoneham, Mass. under thetrademark 880) having a rotating element 140 (attached by set screw 142to shaft 20) and a corresponding stationary element 74 held in place byseal gland 144 bolted by bolts 146 to the seal housing. The seal housingis demountably connected by bolts 147 to the backplate 28. The rotatingelement and stationary element bear against one another rotatably atseal surface 148. Seal 76 prevents leakage to the outside of the pump ofany fluid which (instead of being pumped into pump outlet 18) follows afluid path over and behind impeller 14, along cavity 150 on the back ofthe impeller and into the seal housing. Leakage of such fluid from theseal housing is also prevented by static (e.g., O-ring) seal 152(between cover 30 and seal housing 26), seal 154 (between the seal glandand the stationary element of the seal), seal 156 (between the sealhousing and the backplate of the pump housing), and seal 158 (betweenthe impeller and the shaft). Cover 30 permits access to seal 76 andshaft 20 within seal housing 26 for repair, impeller 14 being backed toface 82 before cover 30 is opened to seal chamber 12 from seal housing26. Seal housing 26 may also contain a cooling coil comprising a coil oftubing 170 (e.g., 1/4" or 3/8" in diameter) centered on the axis of theshaft and positioned about seal 76 (there being a larger than usualspace of about 1" between the outer surface of shaft 20 and the innersurface of seal housing 26 which can also accommodate electronicpressure and temperature transducers). The ends of tubing 170 passthrough and are held by cover 30 and the ends form entrance and exitopenings 172, 174, (FIG. 6) outside cover 30. Cooling fluid can bepumped through the cooling coil to cool the seal.

Referring to FIG. 7, alternatively a flushing coil 176 (similar in sizeand configuration to the cooling coil) can be attached to cover 30. Theflushing coil has a number of holes 178 through which flushing fluid(pumped into the flushing coil) is sprayed into the seal housing toflush it during pump operation.

Flushing of the seal housing can alternately be accomplished throughflushing apparatus comprising a flushing tube 180 (FIGS. 5, 6 and 7)having an entrance end 182 outside of the seal housing and an exit end184 extending through a side wall of the seal housing and oriented todirect flushing fluid into the seal housing in a direction having acomponent tangential to the interior of the side wall of the housing andin a plane normal to the shaft axis. The flush tube enters the sealhousing at the rear end of the housing next to the seal gland whichassures that the entire seal housing will be thoroughly flushed. Thetangential orientation enables the fluid to follow the natural curvatureof the inside wall, and prevents flushing fluid from striking the sealdirectly, which reduces vibration and wear and assures efficient sealoperation while flushing.

Because of its demountable connection, seal housing 26 can be easilyreplaced with housings of any other desired configuration. For example,referring to FIGS. 8, 9, seal housing 26 may be replaced by demountablepacking seal housing 200 (bolted onto backplate 28) which has a steppedinterior surface 202 and is closed at its back end by a seal gland 204which is adjustably bolted on by bolts 206. Gland 204 has a centralclearance hole 205 (through which shaft 20 passes) and a radiallyextending sealing wall 208 facing towards the impeller. A cylindricalrotary member 209 (fixed on shaft 20) has a corresponding radiallyextending sealing wall 210 which has an inner flange 212 close to theshaft and an outer flange 214 spaced apart from the shaft so thatsealing wall 210 and flanges 212, 214 form a recess in which ropepacking 216 (e.g., 3/8" or 5/16" by 22" long) can be spirally wrapped.The radial spacing of the two flanges is at least twice the packingthickness. The axial extent of the flanges is less than the packingthickness so that as gland 204 is tightened down using bolts 206, thepacking is compressed axially between the sealing walls 208, 210.Packing 216 nowhere touches shaft 20 and so causes no wear of the shaft.Packing 216 is held fixed on rotary member 209 so the sealing surface isbetween wall 208 and packing 216. Alternatively, the flanges can be partof the seal gland, the packing can be held fixed in the sealing glandand the sealing surface can be defined between sealing wall 210 and thepacking. The space within the seal housing is sealed against leakage bystatic O-ring seals 218 (between seal gland 204 and seal housing 200),220 (between the front outer wall of seal housing 200 and backplate 28),and 22 (between the rear end surface of the impeller and the rearradially inwardly extending surface 226 of rotary member 209). Rotarymember 209 extends along shaft 20 from seal gland 204 toward impeller 14and is provided at its end adjacent backplate 28 with a helicallythreaded outwardly facing labyrinth seal 230 closely spaced to, e.g.,0.005 inch away from, facing inner surface 232 of the seal housing. Thehelical labyrinth seal 230 hydrodynamically pumps fluid outwardly fromthe seal housing upon rotation of the shaft, reducing fluid pressurewithin the seal housing.

Referring to FIGS. 2, 3, for locking shaft 20 against rotation duringrepair work, removable shaft lock 240 (shown in broken lines) may beemployed which has a central hole which fits over shaft 20 the holehaving a key 242 which mates with a keyway 244 provided in shaft 20. Theouter periphery of the shaft lock has a pair of holes 246 correspondingto threaded holes on the back face of the bearing cartridge for boltingon the shaft lock to prevent rotation of the shaft assembly.

Other embodiments are within the following claims.

What is claimed is:
 1. A centrifugal pump comprising a bladed impellerin a stationary pump housing, the leading edges of said blades beingadjacent a first radially extending wall of said housing, a rotatableshaft on which said impeller is mounted, a shaft support for rotatablyholding the end of said shaft which is opposite said impeller, andadjustable fastening means for connecting said shaft support to astationary member, said impeller, shaft and shaft support together beingadapted for axial adjustment upon axial adjustment of said fasteningmeans, said fastening means comprising at least two threaded boltsprojecting from said stationary member in a direction parallel to theaxis of said shaft, and reference nuts for fixing the position of saidshaft support on said bolts, said reference nuts having marks at regularangular intervals, and at least one reference mark on said shaft supportadjacent each reference nut cooperating with said marks on saidreference nuts for indicating the axial position of said impeller withrespect to said pump housing.
 2. The centrifugal pump claimed in claim 1in which said impeller has a radially extending face opposite saidleading edges, said pump housing further comprises a second radiallyextending wall adjacent said face, and an annular seal is positionedbetween said face and said second wall to seal against said second wallwhen said impeller is withdrawn from said first wall to said secondwall.
 3. The centrifugal pump claimed in claim 2 in which said seal ismounted on said impeller face.
 4. The centrifugal pump of any one ofclaims 1-3 in which there are two said bolts spaced apart on oppositesides of said shaft.